摘要:

Computer simulations of length-weight data indicated that the error incurred by estimating mean weight from mean length is a function of the exponent in the length-weight relationship and the coefficient of variation in the length-frequency distribution. Errors were less than 10% for exponents up to 4.0 if the coefficient of variation were less than 0.1, but error increased to near 90% of actual mean weight for large exponents and coefficients of variation. Similar errors arise for other exponential relationships, such as length-fecundity, that commonly are developed in fisheries work.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<319:EIEMWA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The total length (L, mm)-weight (W, g) relationship for 153 blue suckers (Cycleptus elongatus) collected from areas of swift current in Pool 20, Mississippi River, was log10W = −6.69 + 3.59(log10L). Condition factors (K = 105W/L) were 0.74−1.1; they increased with increasing fish size, and varied among months (March-October) and between years (1977–1978). Fin rays had more discernible annuli than scales after age VII. The largest blue sucker collected was age X (scales) or XIII (fin rays) and 817 mm long. Males generally reached sexual maturity at age IV, females at age VI. Males had nuptial tubercles during April, but no ripe females were found. For six females aged VI-IX (617–736 mm), the fecundity (Y, number of 1-mm diameter eggs)-length relationship was Y = −375,100 + 771.5L. Blue suckers ate primarily Tricoptera and Diptera larvae and pupae, and lesser numbers of Ephemeroptera larvae and amphipods.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<323:BNOBSI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Late larval stages of the Pacific herring, Clupea harengus pallasi, which normally swim in schools, were reared in isolation from conspecifics to determine if schooling behavior is a requirement for metamorphic development. There were no mortalities resulting from prevention of schooling.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<327:STMOPH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The accuracy of a population estimate made by the Leslie removal method was evaluated for adult northern pike (Esox lucius) in a 288-hectare lake. The Leslie estimate of 6,290 fish was within 1% of that obtained from direct enumeration.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<329:LPEFAL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Agricultural drainage development in southwestern Minnesota involves installation of tiles to drain subsurface waters, creation of tributary ditches, and channelization of existing streambeds. The presence, abundance, and diversity of fishes collected in downstream unmodified areas of drainage-developed and undeveloped streams indicate that any downstream impacts are much less severe than impacts demonstrated by others within developed areas. These natural areas appear to serve as reservoirs for stream biotas and should be preserved as refuges for fish species inhabiting those streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<332:DNAARF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Upper lethal temperature ranges for two strains of Lahontan cutthroat trout (Salmo clarki henshawi) were 18.5–20.2 C in Pyramid Lake water (bicarbonate alkalinity, 1,487 mg/liter), 20.2–21.1 C in Dunn Hatchery well water (357 mg/liter), and 21.8–23.0 C in Truckee River water (69 mg/liter). Within each lethal temperature range, the Summit Lake strain was slightly more resistant to heat death than the Marble Bluff strain.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<336:ULTROL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A triggering circuit is described for direct-current fish shockers employing thyristors. Pulse rate can be switched from one to 200 pulses/second in over 200 discrete steps while duty cycle can be varied continuously from 8 to 92%. Adjustments of rate and duty cycle are wholly independent of one another.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<340:IPTFE>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/00028487.1980.10493206

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor